One vertex per element, one color per generator, with an edge from x to x·s.
(5,6)(7,10)(8,9)(11,12)(13,14)(15,21)(16,24)(17,22)(18,19)(20,23)(25,26)(27,28) involution — undirected(1,2)(3,4)(6,9)(10,12)(13,15,17,18)(14,19,22,21)(16,23,27,26)(20,24,25,28)(2,4)(13,16,17,27)(14,20,22,25)(15,23,18,26)(19,24,21,28)(2,4)(13,14)(15,19)(16,25)(17,22)(18,21)(20,27)(23,28)(24,26) involution — undirected(5,7,8,11)(6,10,9,12)(13,15,17,18)(14,21,22,19)(16,26,27,23)(20,24,25,28)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.